He was born into an Ulster aristocratic family at St James's, Westminster, and served for less than a year as a representative in the Irish House of Commons for Carrickfergus before succeeding his father as Marquess of Donegall in 1799 and the proprietor of Belfast.. Lord Donegall was admitted to the Irish Privy Council in 1803 and later served as Lord Lieutenant of County Donegal from 1831 until his death.

He was also made a Knight of the Order of St Patrick in 1821 on the occasion of King George IV's visit to Ireland[1][2] In Belfast, those who had engaged in the reform and patriotic politics of the 1790s remained critical of Donegall's role as the town's pocket borough master.

In 1810, Donegall leased the land, and laid the foundation stone, for William Drennan's progressively conceived Belfast Academical Institution.

[5] In 1809, he leased land on the east side of Donegall Street for building the town's second Roman Catholic Church, St Patricks.

[6] A lifelong gambler, Lord Donegall married the daughter of Edward May, a moneylender and owner of a gambling house.